Our increasingly mobile and mechanized society uses a variety of different fuels (e.g., gasoline, diesel fuel, ethanol, etc.) as energy. Liquid fuels are generally stored in liquid reservoirs such as underground storage tanks, above ground tanks, or any of a variety of different containers. Typically, liquid fuel reservoirs have inlets and outlets through which fuel can be added to and/or removed from the reservoir. These inlets and outlets may typically consist of a riser pipe extending from the reservoir. Internal to the riser pipe is a drop tube that typically includes an overfill valve adapted to respond once a predetermined level is reached in the liquid reservoir. To simplify manufacture and assembly, it is also known to provided the drop tube in a plurality of segments that are fastened together in series to form an overall drop tube assembly. As shown in U.S. Pat. No. 4,986,320, for example, the drop tube assembly includes an intermediate drop tube segment having opposed ends that are each correspondingly fastened to an upper and lower drop tube segment with fasteners extending through the respective walls of the segments.
Such configurations have proven to be very effective. To further enhance the beneficial nature of previous drop tube assemblies, there is a desire to provide a substantially fluid tight seal at the fastening location between the drop tube segments. A fluid tight seal may reduce or prevent fluid, such as vapor, from being released from the ullage area of the reservoir to the interior of the drop tube that might act as a chimney to vent the fluid to the surrounding atmosphere and potentially create an environmental concern.
To address potential concerns of vapor leakage, it is known to provide fastening sections with an epoxy layer to provide a fluid-tight seal at potential leak points. For example, it is known to provide a drop tube assembly, as shown in U.S. Pat. No. 4,986,320, with a fastening arrangement as shown in FIGS. 15A or 15B of the drawings herein. Each conventional fastening arrangement illustrated in FIGS. 15A and 15B includes a layer of Loctite® epoxy-sealant for use as a cold weld bonding compound. As shown in FIG. 15A, a first drop tube segment 400 is known to include a first fastening section 402 with a tapered exterior threaded portion 408. A second drop tube segment 420 is also known to include a second fastening section comprising an adapter 424 that is fastened to an end of a tubular member 422 at a weld seam 423. The adapter 424 includes a tapered interior threaded portion 428 that threadedly engages tapered exterior threaded portion 408 of the first drop tube segment 400. In order to provide a fluid-tight seal, an epoxy layer 410 may be applied between mating portions of the threaded portions.
FIG. 15B illustrates another conventional fastening arrangement that includes a first drop tube segment 500 including a first fastening section 502 including a groove 508 receiving a resilient O-ring 506 and a shoulder 504 that acts as a registration stop for a second drop tube segment 520. The second drop tube segment 520 is also known to include a tubular member 522 that is inserted over the first fastening section 502 until an end of the tubular member 522 abuts the shoulder 504 of the first fastening section 502. A fastener 512 is inserted through an aperture 524 in the tubular member 522 to engage an aperture 509 defined in the first fastening section 502. In order to provide a fluid seal, an epoxy layer 510a may be applied to the first fastening section 502 prior to assembly of the first and second drop tube segments. The epoxy layer 510a is often required due to inconsistencies in the clearance between outer dimensions of the first fastening section 502 and inner dimensions of the tubular member 522. Any inconsistencies may be caused by imperfections in the outer end and/or damage to the outer end of the tubular member 522 due to the typically thin aluminum walls of the tubular member 522 which render the outer ends prone to deformation. Another epoxy layer 510b may also be applied to the area over and about the head of the fastener 512 to prevent fluid leakage through the apertures 509, 524.
Application of an epoxy layer to provide fluid-tight sealing has proven very beneficial to reduce fluid vapor leakage. However, the addition of an epoxy layer typically greatly lengthens the installation process and the epoxy layer must cure for an extended period of time before the drop tube assembly may be installed with respect to the liquid reservoir. Currently, there is a need for drop tube assemblies that comprise a plurality of sections that may be connected together for immediate installation with respect to the liquid reservoir while providing a fluid seal at the fastening location between the drop tube segments.